Ventilating paint booths



June 23, 1964 B. AKE LARSSON ETAL 3,138,087

VENTILATING PAINT BOOTHS Filed May 11, 1961 2 Sheets-Sheet l INVENTORSI EV RT KRANTZ BENGT KE LARSSON ATTYS.

June 2 1964 B. AKE LARSSON ETAL 3,138,037

VENTILATING PAINT BOOTHS Filed May 11, 1961 2 Sheets-Sheet 2 FIGZ.

INVENTORS EVERT KRANTZ BENGT AKE LARSSON BY WW ATTYS.

United States Patent 3,138,087 a VENTILATIING PAINT BOOTHS Bengt Ake Larsson, Naeka, and Evert Krantz, Stockholm,

Sweden, assignors to Akliebolaget Svenska Fliiktfabriken, Stockholm, Sweden Filed May 11, 1961, Ser. No. 109,297 Claims priority, application Sweden May 12, 1960 4 Claims. (Cl. 98-115) The present invention relates to ventilating paint booths, and has particular application to ventilating paint booths in which the work pieces to be painted are conveyed continuously or intermittently through the booth and are painted by spray painting equipment.

A primary object of the present invention is to provide apparatus for effectively ventilating the paint booths, which at the same time, minimizes the depositing of the paint on the walls of the booth and for effectively cleaning the exhausted ventilating air.

More specifically, the present invention provides a paint booth having means to uniformly distribute the supplied air over the entire horizontal cross section of the booth at the top of the booth and including generally V-shaped bottom walls converging into a longitudinal slot for exhausting the ventilating air. The slot communicates directly with the inlet channel of a drop separator which is operable to separate the paint drops from the ventilating air and exhaust the cleansed air.

The present invention provides means for introducing washing liquid into the booth so as to cause it to flow down the V-shaped walls and form a covering liquid film thereon. In accordance with another feature of the invention, supplemental liquid is introduced into the inlet channel of the drop separator to form a covering liquid film on the side walls thereof.

In the preferred embodiment of the present invention, the inlet channel of the drop separator forms a Venturi channel which is provided at its throat with an inwardly projecting throttling flange which deflects the liquid film from the V-shaped walls of the booth into the exhausted ventilating medium in said throat and furthermore the supplemental washing liquid may be supplied immediately downstream of said throttling flange.

The present invention also provides an improved drop separator chamber wherein the exhausted ventilating medium is deflected by drop-trapping deflecting screens whereby the drops of paint and washing liquid are separated from the medium.

In paint booths where manual spray painting is performed in selected sections and electrostatic spray painting in the remaining sections, the ventilating air inlets and outlets are coextensive with the manual spray-painting sections, the washing liquid in the electrostatic spraypainting sections being discharged through the outlet underlying the manual spray-painting sections.

All of the objects of the present invention are more fully set forth hereinafter with reference to the accompanying drawing wherein:

FIG. 1 is a view in side elevation at a reduced scale showing an elongated paint booth made in accordance with the present invention; and

FIG. 2 is a partly schematic sectional View taken on the line 2-2 of FIG. 1.

Referring to the drawing, the apparatus illustrated therein comprises an elongated paint booth I having a central conveyor 21 operable to carry the work pieces 2 longitudinally through the channel. On opposite sides of the conveyor 21 are foraminous work platforms 22 and 23 for supporting the painters 24 who operate the spray guns for painting the work pieces 2. Below the conveyor 21, the paint booth 1 is provided with V-shaped bottom walls which converge downwardly and depend ice from the longitudinally extending, spaced side walls as shown. Ventilating air is introduced into the paint booth I by ducts 3 which may be controlled by throttling dampers 25. As shown in FIG. 2, the bottom walls 5 converge into an outlet slot 6 which is coextensive with the inlet ducts 3.

In accordance with the present invention, means is provided to insure uniform distribution of air over the entire cross section of the paint booth. To this end, the roof of the booth 1 below the inlet ducts 3 is formed by air filters 4, which extend over the full width of the booth I. The air supplied through the ducts 3 may be heated prior to passage through the filters 4. 30 designates lamps in the upper corners of the booth.

In order to prevent depositing of the paint spray on the bottom walls 5 of the booth 1, means defining a liquid inlet which extends longitudinally of the walls 5 is provided to flow a continuous liquid film over the entire surface of the bottom walls 5. To this end, liquid troughs 26 are provided on opposite sides of the paint booth at the upper extremities of the bottom walls 5. Weirs or dams 10 are provided to cause the liquid in the reservoir to flow down the bottom walls 5 in the form of a continuous, flowing liquid film.

In accordance with another feature of the invention, the air being discharged through the slot 6 passes directly into the inlet channel 7 of a drop separator 8 which is coextensive with the slot 6. In the present instance, the inlet channel 7 and the V-shaped bottom walls define a Venturi passage with throttling flanges 12 positioned in the throat thereof to atomize the liquid film by deflecting it into the air being exhausted through the slot 6. The bottom portion of the drop separator 8 forms a collecting channel 13 which receives the drops of washing liquid and paint separated from the exhausted ventilating medium and discharges the same into a flotation tank 14 by means of a conduit 15. The bottom wall of the separator 8 is continuously covered with a thin liquid film by a supply reservoir 33. Deflecting screen walls 16 are mounted as shown in FIG. 2 to deflect the ventilating medium into a tortuous path and trap the drops therefrom prior to discharge of the medium through exhaust ducts which are connected to an exhaust fan or other suitable exhaust means 27.

In order to insure against depositing of the paint spray on the inlet channel 7 of the drop separator 8, means is provided to flush the walls thereof with a continuous flowing film of washing liquid. To this end, secondary reservoirs for washing liquid are provided at 28 on opposite sides of the throat of the Venturi passage. Narrow slots 11 are formed in the walls 32 of the inlet channel 7 immediately downstream of the throttling flanges 12 to form a continuous film which flows downwardly along the side walls 32 to prevent the depositing of paint thereon. The film on the walls 32 is discharged into the collecting channel 13 of the separator and is carried into the flotation tank 14. The liquid in the flotation tank 14 is passed through a suitable filtering device 17 and is pumped by a circulation pump 18 and distribution conduits 19 to the reservoirs 26, 28, and 33 for recycling through the system.

In plants where the paint booth is used for both manual spray painting and electrostatic spray painting, it is desirable to reduce the circulation of ventilating medium through the electrostatic spray painting sections. To this end, as shown in FIG. 1, the booth I is divided into separate sections 35, 36, and 37, in the present instance, three, the central section 36 housing the electrostatic spray painting equipment. The air is introduced and exhausted only into the sections 35 and 37 for manual spray painting and the washing liquid which flows down the walls 5 in the electrostatic section 36 is discharged into the slot 6 in the adjacent manual spray painting sections 35 and 37. It is understood of course that where the spray paint is manual throughout the paint booth, the inlet ducts 3, the outlet slot 6 and drop separator 3 would be coextensive with the entire length of the spray booth 1.

While a particular embodiment of the present invention has been herein illustrated and described it is not intended to limit the invention to such disclosure, but changes and modifications may be made therein and thereto within the scope of the following claims.

What we claim is:

1. In combination, a spray painting booth having spaced, longitudinally extending side walls with means defining ventilating air inlets connected to the upper portion of said side walls to direct a ventilating air stream downwardly therebetween, each of said side walls having a downwardly depending bottom wall, said bottom walls converging so as to be substantially V-shaped in cross section and terminating in an elongated slot having inwardly projecting flanges forming a throat section, and means to cause said ventilating air to move through said slot from said ventilating air inlets; a drop separator chamber for the ventilating air underlying said slot, and having an air exhaust means at the upper portion of said chamber and a liquid removing means at the lower portion of said chamber, having an inlet channel, said inlet channel having a pair of spaced diverging side Walls depending from opposite sides of said slot; and liquid supply means having means defining a liquid inlet extending longitudinally along both of said depending bottom walls along the upper edges thereof and adapted to supply a continuous thin film of liquid on said V-shaped bottom walls flowing downwardly toward said slot, said inlet channel and said V-shaped walls forming a Venturi passage, flanges projecting into the throat of said Venturi passage substantially transverse to the direction of flow of said entering air stream so that the continuous film of liquid flowing downwardly toward said slot is injected into said entering air substantially perpendicular to said entering air thereby allowing atomization of said liquid, said liquid supply means adapted to form a continuous film on the side walls of said inlet channel flowing downwardly into said drop separator to thereby protect said booth bottom walls and said inlet side walls from the deposit of paint spray entrained in said ventilating air.

2. Apparatus according to claim 1 wherein said liquid supply means and said means defining a liquid inlet comprise separate troughs located at the top of said V-shaped bottom walls and co-extensive with said bottom walls.

3. Apparatus according to claim 1 wherein said Venturi passage includes separate liquid supply means incorporating means defining narrow slots in said diverging side walls adjacent to said throttling flanges so as to form a continuous flowing liquid film on the diverging side walls of said Venturi passage.

4. Apparatus according to claim 1 wherein said air exhaust means includes discharge conduits opening thereinto above the lower terminal end of said inlet channel, a liquid supply reservoir at the bottom of said drop separator adapted to supply a thin film of liquid along the bottom of said drop separator, said ventilating air progressing downwardly and striking said film covered bottom of said drop separator thereby deflecting said ventilating air, drop-trapping screen walls projecting into said drop separator so as not to interfere with said downwardly progressing ventilated air, said drop-trapping screen walls deflecting the deflected ventilating air into a tortuous path from said film covered bottom to said discharge conduits thereby causing drop separation.

References Cited in the file of this patent UNITED STATES PATENTS 907,633 Narowetz Dec. 22, 1908 1,062,446 Ernst May 20, 1913 1,637,597 Ulrici Aug. 2, 1927 1,926,433 Cartmell Sept. 12, 1933 2,086,514 Saunders et al July 6, 1937 

1. IN COMBINATION, A SPRAY PAINTING BOOTH HAVING SPACED, LONGITUDINALLY EXTENDING SIDE WALLS WITH MEANS DEFINING VENTILATING AIR INLETS CONNECTED TO THE UPPER PORTION OF SAID SIDE WALLS TO DIRECT A VENTILATING AIR STREAM DOWNWARDLY THEREBETWEEN, EACH OF SAID SIDE WALLS HAVING A DOWNWARDLY DEPENDING BOTTOM WALL, SAID BOTTOM WALLS CONVERGING SO AS TO BE SUBSTANTIALLY V-SHAPED IN CROSS SECTION AND TERMINATING IN AN ELONGATED SLOT HAVING INWARDLY PROJECTING FLANGES FORMING A THROAT SECTION, AND MEANS TO CAUSE SAID VENTILATING AIR TO MOVE THROUGH SAID SLOT FROM SAID VENTILATING AIR INLETS; A DROP SEPARATOR CHAMBER FOR THE VENTILATING AIR UNDERLYING SAID SLOT, AND HAVING AN AIR EXHAUST MEANS AT THE UPPER PORTION OF SAID CHAMBER AND A LIQUID REMOVING MEANS AT THE LOWER PORTION OF SAID CHAMBER, HAVING AN INLET CHANNEL, SAID INLET CHANNEL HAVING A PAIR OF SPACED DIVERGING SIDE WALLS DEPENDING FROM OPPOSITE SIDES OF SAID SLOT; AND LIQUID SUPPLY MEANS HAVING MEANS DEFINING A LIQUID INLET EXTENDING LONGITUDINALLY ALONG BOTH OF SAID DEPENDING BOTTOM WALLS ALONG THE UPPER EDGES THEREOF AND ADAPTED TO SUPPLY A CONTINUOUS THIN FILM OF LIQUID ON SAID V-SHAPED BOTTOM WALLS FLOWING DOWNWARDLY TOWARD SAID SLOT, SAID INLET CHANNEL AND SAID V-SHAPED WALLS FORMING A VENTURI PASSAGE, FLANGES PROJECTING INTO THE THROAT OF SAID VENTURI PASSAGE SUBSTANTIALLY TRANSVERSE TO THE DIRECTION OF FLOW OF SAID ENTERING AIR STREAM SO THAT THE CONTINUOUS FILM OF LIQUID FLOWING DOWNWARDLY TOWARD SAID SLOT IS INJECTED INTO SAID ENTERING AIR SUBSTANTIALLY PERPENDICULAR TO SAID ENTERING AIR THEREBY ALLOWING ATOMIZATION OF SAID LIQUID, SAID LIQUID SUPPLY MEANS ADAPTED TO FORM A CONTINUOUS FILM ON THE SIDE WALLS OF SAID INLET CHANNEL FLOWING DOWNWARDLY INTO SAID DROP SEPARATOR TO THEREBY PROTECT SAID BOOTH BOTTOM WALLS AND SAID INLET SIDE WALLS FROM THE DEPOSIT OF PAINT SPRAY ENTRAINED IN SAID VENTILATING AIR. 